1. Field of the Invention
The present invention relates to an accumulator device for use In an air-conditioning system, and more particularly to an accumulator device for use in an air-conditioning refrigeration system of a motor vehicle.
2. Description of the Prior Art
The use of accumulator devices in air-conditioning systems, particularly motor vehicle air-conditioning systems, is well known. It is also well known to use steel or aluminum in manufacturing an accumulator housing. However, it is less common to use plastic in manufacturing accumulator housings since environmental and performance requirements require use of prohibitively thick plastic walls.
In a typical air-conditioning system, the compressor receives a gaseous refrigerant from the evaporator and compresses the gaseous refrigerant, sending it under high pressure to the condenser as a superheated vapor. Since the high-pressure vapor delivered to a condenser is much hotter than the surrounding air, the heat of the high-pressure vapor is given off to the outside air flowing through the condenser fins, thereby cooling the refrigerant. As the gaseous refrigerant loses heat to the surrounding air, it condenses into a liquid refrigerant. The condensed liquid refrigerant then enters an orifice tube at which the pressurized liquid refrigerant transforms into a gaseous state thereby absorbing heat from warm air passing through the fins of the evaporator.
After the warmed liquid refrigerant changes phase to gas, it is passed from the evaporator to an accumulator. From the accumulator, the refrigerant is passed back to the compressor to start the cycle over again. However, it is very important to ensure that the refrigerant being passed back to the compressor is in a completely gaseous state. If liquid refrigerant reaches the compressor, it will clog it up. Thus, the accumulator'main purpose is to assure that only gaseous refrigerant passes to the compressor. Additionally, the accumulator injects a prescribed amount of lubricating oil into the gaseous refrigerant for lubricating the compressor. Furthermore, the accumulator can be used to make sure the oil-laden gaseous refrigerant is free of particulates that might also harm the compressor.
Accordingly, the accumulator of an air-conditioning system can be used to accomplish five functions, it (a) completely vaporizes the refrigerant, (b) removes all water vapor, (c) traps all particulates, (d) injects a lubricant into the outgoing refrigerant vapor stream, and (e) acts as a reservoir for the refrigerant when system demand is low. Typical examples of accumulators accomplishing these functions are shown in U.S. Pat. Nos. 3,798,921; 4,111,005; 4,291,548; 4,496,378; 5,052,193; and 5,282,370.
Typically, a suction accumulator consists of a liquid storage vessel in which is received a generally U-shaped tube, one end of which is connected to the outlet of the storage vessel and the other end of which is opened to the interior of the vessel. As the incoming liquid refrigerant flows into the vessel, it collects in the bottom of the interior and the gaseous components of the refrigerant are forced, due to pressure in the accumulator and the vacuum created by the compressor, through the open end of the U-shaped tube and out of the accumulator. Oil for lubricating the compressor collects in the bottom of the vessel along with any liquid refrigerant. Typically, an orifice located in a bight portion of the U-shaped tube entrains, by venturi action, a metered amount of oil into the gaseous refrigerant exiting the accumulator.
A problem with prior art accumulators is that it is necessary to introduce some type of device, such as a refrigerant separator member, to prevent substantial amounts of liquid refrigerant from exiting the accumulator or gaining access to the open end of the U-shaped tube. Thus, it is customary to employ a refrigerant separator member somewhere proximate the open inlet end of the U-shaped tube in order to prevent the liquid from entering the exit tube of the accumulator. Typically, these refrigerant separator members have a frustoconical design that serves to deflect the liquid refrigerant back down into the bottom portion of the accumulator while allowing the gaseous refrigerant to pass by.
An example of such a device includes U.S. Pat. No. 4,474,035 to Amin et al. Amin et al. disclose a domed refrigerant separator located in an upper region of an accumulator housing adjacent an accumulator inlet opening. Liquid refrigerant enters the accumulator housing through the inlet opening in the top of the housing and disperses over the dome of the refrigerant separator toward the sides of the housing. This creates vertical flow of the refrigerant down the sides of the accumulator housing. The vapor component of the refrigerant collects in the upper region of the housing beneath the refrigerant separator, near the inlet end of an outlet tube. Amin et al. disclose that an inlet end of an outlet tube is located directly below the domed refrigerant separator. Amin et al. further disclose that a leg of the outlet tube is brazed or welded in a hole in the refrigerant separator as well as to the top of the accumulator housing.
Accordingly, traditional prior art accumulator references uniformly disclose and teach the use of a refrigerant separator member. The refrigerant separator member prevents liquid refrigerant from reaching an exit tube that is partially located within the accumulator and that is used to convey the gaseous refrigerant it to the compressor. The components, such as the exit tube and the refrigerant separator member, necessary to achieve the stated functions of an accumulator, add significantly to the cost, complexity and potential problems associated with prior art accumulators.
One recent approach to solving Such problems with traditional accumulators is represented in U.S. Pat. No. 5,471,854 to DeNolf. DeNolf teaches use of an accumulator that does not have a refrigerant separator member or tubes within a housing. DeNolf discloses the accumulator as having an inner housing with standoffs disposed within an outer housing thereby defining a flow path therebetwcen. A cap seals the inner and outer housings and connects the accumulator to an air-conditioning system. A refrigerant is introduced to the inner housing and flows through an aperture in the inner housing into and through the flow path down one side of the accumulator, across the bottom of the accumulator, back up an opposite side of the accumulator, and out the accumulator via a passage in the cap.
While the DeNolf reference represents a very significant improvement over the structure of traditional accumulators, it unfortunately involves a few drawbacks. For one, the DeNolf reference involves multiple housings that must be individually formed and further processed. Additionally, a rather rigid material, Such as aluminum, must be used in order to withstand the internal forces due to pressure within the refrigeration system and the external forces imposed upon the accumulator during assembly. Therefore, cheaper and lighter weight materials such as plastic are not generally usable with such a design. Finally, the DeNolf reference does not disclose structure for shielding the aperture in the inner housing from incoming liquid refrigerant.
Thus, there remains a need for an accumulator for use in an air-conditioning system of an automotive vehicle, that is adaptable to plastic materials, is more capable and more reliable in preventing liquid refrigerant from reaching the inlet line of the compressor, and wherein the accumulator does not require the use of an exit tube such as is known in the prior art. The use of plastics and the elimination of the tube and multiple housings of the prior art would result in significant cost savings in the manufacture of the accumulator.